This invention relates to ultrasonic nondesctructive testing. More particularly, the invention concerns a defect gate which obtains data regarding defects in a test specimen and which can be interfaced with a computer for control of the inspection parameters and for analysis and diagnosis of the data.
Ultrasonic nondestructive evaluation techniques are based on transmission and reflection of acoustic energy in a material under test. Interrogating signals are transmitted to a material specimen and reflected from discontinuities therein, which may be indicative of defects in the specimens. In conventional ultrasonic inspection of materials, an operator manually adjusts the instrumentation parameters while observing a display of the transmitted and/or reflected signal characteristics. To distinguish those signal characteristics indicative of specimen defects the operator synchronizes a defect gate "window" with a signal to detect only indications from the region of interest in the specimen being inspected. The gate window corresponds to a depth range in the test specimen. Precise adjustment is often required, as when defects may occur very near the front and rear specimen surfaces and/or where the geometry of the specimen under test is such that reflection from "valid" discontinuities within the specimen may be expected. The operator also manually adjusts the defect gate "level" above which a defect indication is regarded as significant.
During the ultrasonic inspection process the operator must continually monitor the indications obtained and readjust various settings. This obviously results in a slow and expensive procedure subject to human errors, lack of repeatability and limited data analysis and diagnostics.
To some extent the human operator has been supplemented by automatic data gathering and control procedures which may involve the use of a computer. Typically, data as to a defect detected within a gate window is converted to digital form and made available to a computer. Again, however, where complex specimen geometries are involved and defects may occur close to valid discontinuities, the problem of distinguishing a defect from such a valid discontinuity remains. The data captured may prove, upon analysis, to be from a valid discontinuity. Further, in case of multiple defects which are relatively closely spaced and within the same gate window, only one such defect will be captured.